Well, for me it's a stupid idea indeed, and I guess that when CZ said "if you can't hold, you can't be rich" he was directing that saying to peeps like you, buying at current market price does not necessarily mean buying high most especially, for a coin that has the potential to still appreciate in price.
If for example you buy a coin at 1$, and price pumps to $1.5 and you sell, what if after let's say 2 years, the price already climbed to $50 per coin, how would you feel knowing fully well you dumped your bag of that coin at just $1.5?
HOLD IS KING, and those who said it aren't stupid to say that.
That is not a "stupid" thing to do. You take your profit when you are ready. What the use if you keep on holding and never sell or use your coins? You don't want to sell because you think after two years, the price will climb to $50 and you don't want to miss the opportunity. If that is the case, then you will never be able to sell because you might then think "what if the price goes to $100". You don't have to keep holding. It is okay to take your profit. Take your profit, if the price falls, buy more, hold and then sell.